The invention relates to printing apparatus and particularly to the aspect of such apparatus for applying ink to a surface on which an image is disposed which is to be applied to another surface. While the invention has particular application to flexotype apparatus and particularly to such apparatus utilized for marking wood based panel sheets which typically may be 4'.times.8' and 1/4" to 3/4" thick. Examples include plywood, particle board, wafer board and oriented strand board. It will be understood the invention also has application to other printing apparatus. In flexotype printing apparatus, ink disposed on a first roller is applied to a second roller on which an image is disposed. The image on the second roller is then passed over the panel or other surface on which the image is to be printed. This is in contrast to offset printing in which print ink on a first roller is applied to a second roller which is then applied to a roller on which the image to be printed is disposed.
In the lumber and panel industry there is a requirement to identify individual pieces of lumber and panels with grade and identification markings. Some prior art apparatus does use a roll which has a substantially solid circumferential face in which the ink is disposed. This arrangement is in contrast to liquid ink feeding apparatus. The ease with which the ink is transferred to the printing element or image before it is transferred from the image to a piece of lumber is of great importance. If proper inking occurs, the ink is transferred and a complete image will be produced on the lumber. If too much or too little ink is transferred, the printing will be illegible on the wood product.
A difficulty which is particularly acute in the marking of warped plywood panels that in such printing is the cylindrical printing drum is customarily mounted on an axis of rotation which is fixed and the printing drum is pulled into contact by a single, centrally located air cylinder connected by a yoke to the drum shaft at both ends. The ink drum passes over the warped plywood panel or other irregular surface on which a printed image is to be placed is incomplete, non-uniform, smudged, or otherwise illegible. Illegible markings are unacceptable in the wood products industry as well as in many other applications where marking is to be placed on an irregular surface.
It is an object of the present invention to provide printing apparatus which will consistently produce sharp, clear, uniform, and complete printed images on irregular surfaces, and improves the printed images on regular surfaces.
It is still another object of the invention to provide apparatus which is particularly adapted for use in printing images on warped lumber and particularly warped wood based panels.
It is another object of the invention to provide apparatus which will have reliability and image definition which is for greater than existing apparatus.
It is still another object of the invention to provide apparatus which will react quickly to produce a clear and complete image even if the relative speed between the printing drum and the irregular material upon which the printing is occurring it is quite high.